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Ocular Motility > Fixations and Visual Attention > Flashcards

Fixations and Visual Attention Flashcards

1
Q

T/F The eye is NEVER motionless

A

true

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2
Q

What is the functional fovea area?

A

+/- 30’ of arc discrete area on the retina within which images are held

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3
Q

What happens to the discrete area on the retina the longer fixation is held?

A

longer fixation=larger area

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4
Q

What are three types of movements (subconscious)

A

tremors, drifts, and micro saccades

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5
Q

What is a tremor?

A

constant, high frequency 30-100 Hz, amp 20” of arc, no VA change

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6
Q

What is a drift?

A

low velocity <0.5 Hz, crosses 15 cones/sec, irregular movement

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7
Q

What is a microsaccade?

A

1-2/sec, corrects drift, large dynamic overshoot component, error correcting, amp of 5’ of arc, amplitude dependent relation

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8
Q

Which movement is always binocular?

A

micro saccades

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9
Q

Which movement do eyes perform most of the time?

A

drifts (95%)

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10
Q

Which movement is superimposed over the other two?

A

tremors

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11
Q

What factors impact movements?

A

peripheral gaze direction increases probability of movement, darkness: less steady and more drifts/correcting saccades

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12
Q

During normal fixations, what is the relationship between drift and microsaccades?

A

Drifts and micro saccades move in the opposite direction and drift is error producing and occurs 95% of the time while micro saccades are error correcting

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13
Q

What two things make drifts worse?

A

greater gaze angle and darkness– evidence of leaky neural integrator

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14
Q

What improves accuracy of fixations?

A

visual feedback

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15
Q

Even w/o visual feedback, deviation is typically only a few degrees, what does this suggest?

A

use of EOM proprioception and tactile info from lids

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16
Q

What are the three main types of abnormal fixation movements?

A

slow drift, saccadic intrusion, and nystagmus

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17
Q

What is a slow drift?

A

found with functional amblyopia, amp 1 degree, velocity <3 deg/sec, irregular, slow frequency <0.5 Hz

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18
Q

T/F VT will NOT fix a slow drift

A

false

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19
Q

What is a saccadic intrusion

A

large fixational saccade that interrupt attempts at fixation; three kinds= square wave jerks, macro square wave jerks, and macro saccadic oscillations

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20
Q

What is an aberrant tremor?

A

seen w/ EEG or coma patient because other movements usually cover them; baseline state of brainstem

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21
Q

What is a square wave jerk?

A

away from the target and then back 200 msec later; dx cerebellar disease if freq/amp increases

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22
Q

What is a macro square wave jerk?

A

larger, more frequency duration off target 100 msec; dx cerebellar disease and multiple sclerosis

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23
Q

What is a macro saccadic oscillation?

A

saccadic sequence increasing then decreasing amplitude to either side of a target; ALSO dx cerebellar disease

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24
Q

Which of the abnormal fixation movements might you see in clinic?

A

macro square wave jerks

25
Q

T/F fixation in amblyopia improves with feedback

A

true

26
Q

Explain the feedback received by amblyopic patients in the study

A

goggles w/ a computer program track fixation, and when the eye leaves the target, the computer makes an auditory stimulus until focus is corrected– allowing the patient to learn to control fixation

27
Q

What happens during a fixation?

A

EOMs keep the eyes still with respect to the visual environment as the head/body moves

28
Q

What two systems promote visual stabilization?

A

VOR vestibulo-ocular and OKN optokinetic

29
Q

What prevents image degradation?

A

micro saccades and the troxler effect

30
Q

What is true of the scan path of a photograph under free exploration?

A

most of the focus is on the face and other objects

31
Q

What was the Yarbus free exploration study?

A

subjects typically focus on faces and objects; under command to judge material status look at clothes and servants; under command to judge age differences look at faces and height

32
Q

What is true of an expert viewer as compared to a novice?

A

Expert has fewer fixations, shorter duration, less random search pattern of fixations– uses vision to derive meaning

33
Q

What is the primary purpose of the visual system?

A

to derive meaning and the direction of action

34
Q

What is a “consequence” of visual attention?

A

selection of an area to pay attention to will cause the omission of some other things (figure vs ground) due to limited scope of attention

35
Q

What happens to things we focus on during visual attention?

A

they get amplified in the system, allowing for persistence of their image for further inspection by higher order process

36
Q

Most visual problems are problems of ____ not _____

A

omission not commission

37
Q

What are the components of the visual attention system?

A

attention window and visual buffer, encoding processes, memory, information look up, and attention shifting

38
Q

What is inside the attention window?

A

figure

39
Q

What is in the visual buffer?

A

ground

40
Q

____ emerges from ____

A

figure, ground

41
Q

What is the figure processed by?

A

object properties–what

42
Q

What is the ground processed by?

A

spatial properties– where

43
Q

What does associative memory do?

A

accesses previous info and gives context

44
Q

What happens with attention shifting?

A

restart the process, does not require an eye movement

45
Q

What steps does attention/shape shifting entail?

A

disengage, move, engage

46
Q

T/F we have to have a stimulus to shift attention

A

false, we have volitional control, we can also inhibit a shift of attention to a stimulus

47
Q

Which steps of shape shift change the size of the attention window?

A

disengage and move

48
Q

What step do patients with autism have trouble with?

A

engage

49
Q

What step do patients with parkinsons have trouble with?

A

disengage

50
Q

What step do myopes have trouble with?

A

disengage

51
Q

What step do ADHD patients have trouble with?

A

inhibition

52
Q

What is sensory memory?

A

the what system

53
Q

What is motor memory?

A

the where system

54
Q

Object recognition in human vision is provided by:

A

separate but simultaneous processing and representation of what and where information at high levels of the visual system

55
Q

Frame of reference is attached to…

A

the basic feature at each fixation point and includes what and where data

56
Q

Mechanisms of visual attention use ____ info to direct sequential image processing (what to do next)

A

where– context and planning

57
Q

Mechanisms provide comparisons of ___ and ___ object features in each fixation

A

current and expected

58
Q

How do we look at a face?

A

One eye to the other then down the nose and around the face

Ocular Motility (13 decks)

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